1. The Right Atrium, receives "used blood" from the body. Blood will be pushed through the tricuspid valve to the
2. Right Ventricle, the chamber which will pump to the lungs through the pulmonic valve to the
3. Pulmonary Arteries, providing blood to both lungs. Blood is circulated through the lungs where carbon dioxide is removed and oxygen added. It returns through the
4. Pulmonary Veins, which empty into the
5. Left Atrium, a chamber which will push the Mitral Valve open. Blood then passes into the
6. Left Ventricle. Although it doesn't always look like it in drawings done from this angle, this is the largest and most important chamber in the heart. It pumps to the rest of the body. As it pumps, the pressure will close the mitral valve and open the aortic valve, with blood passing through to the
7. Aorta, where it will be delivered to the rest of the body.

......The right ventricle contracts, and then sends it to the right atrium. The deoxygenated blood from the right atrium, leaves the heart via the pulmonary artery, and then goes to the lungs, where the carbon dioxide is transferred along the capillaries to the Alveoli. The pulmonary vein, then picks up oxygenated blood from the lungs, and transports it to the left side of the heart, where it then is sent to the cells, muscles, and organs of the body. Then the cycle is repeated. This is called the systemic circuit

Navin wrote:Blood from the vena cavae enter the right atrium. It contracts and the blood enters the right ventricle. The right ventricle contracts.

What happens next?

Does the tricuspid valve close first before the opening of the pulmonary valve?

Or is it the other way round?

The entering blood into right ventricle will result in an increasing pressure of right ventricle, which will close tricuspid valve. More blood in right ventricle will close tricuspid valve more tightly, means that blood will never come back to right atrium.

Then, the contraction of right ventricle that comes afterwards will push its content (blood) to flow along the pulmonary arteria. This contraction is rhytmic and pulsatory.

Similar to the condition in right ventricle, the blood pumped into pulmonary arteria then generates pressure that will close the pulmonary valve. Then comes the next blood due to the next pulse generated by the contraction of right ventricle... and so on